The motor cortex and basal ganglia play an important role in the regulation of behavior. Clinical and experimental observations on disease or damage to the motor cortex and basal ganglia have described, among other deficits, marked impairments in the initiation of behavior and in the ability to perform complex cognitive and motor tasks. Recent studies by the applicant have revealed a topographic axio-distal distribution of motor cortex inputs to the caudate nucleus. The proposed electrophysiological experiments will investigate how this axio-distal sorting is mirrored at the level of the globus pallidus and the pallidal output to the thalamus. These experiments will provide valuable information on the organization of the neurological substrates involved in the modulation of axial and distal musculatures in intact animals and in animals with brain lesions. These studies should lead to a better understanding of the normal function of and the effects of lesions on brain systems involved in the initiation of behavior. The results from these experiments will hopefully suggest new procedures for alleviating the disorders produced by disease or damage to these brain systems.